package com.zh.note.leetcode.dp;

/**
 * 115. 不同的子序列
 */
public class LC_115_numDistinct {

    public int numDistinct(String s, String t) {
        //dp[i][j]：以i-1为结尾的s子序列中出现以j-1为结尾的t的个数为dp[i][j]。
        int[][] dp = new int[s.length() + 1][t.length() + 1];
        for (int i = 0; i < s.length() + 1; i++) {
            dp[i][0] = 1;
        }
        for (int i = 1; i < s.length() + 1; i++) {
            for (int j = 1; j < t.length() + 1; j++) {
                if (s.charAt(i - 1) == t.charAt(j - 1)) {
                    dp[i][j] = dp[i - 1][j - 1] + dp[i - 1][j];
                } else {
                    dp[i][j] = dp[i - 1][j];
                }
            }
        }
        return dp[s.length()][t.length()];
    }
}

